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GCSE Physics <3 > Topic 4 – Atomic Structure Fundamentals > Flashcards

Topic 4 – Atomic Structure Fundamentals Flashcards

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1
Q

whats the radius of an atom

A

1 x 10^-10 m

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2
Q

the radius of the nucleus is __________ the radius of the atom

A

less than 1/10000

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3
Q

where do we find electrons

A

energy levels

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4
Q

energy levels which are further from the nucleus are at a ____________ than those close to the nucleus

A

higher energy level

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5
Q

how can an electron change energy levels to move to a higher energy level

A

if the atom absorbs electromagnetic radiation

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6
Q

how can an electron change to a lower energy level?

A

if the atom emits electromagnetic radiation it can return to a lower energy level

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7
Q

What is the mass number

A

the larger number, protons + neutrons

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8
Q

why do atoms have no overall charge?

A

number of electrons is equal to number of protons
so negative charges in electrons cancels out positive charge in protons

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9
Q

whats the atomic number

A

number of protons/electrons

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10
Q

how to calculate neutrons?

A

subtract atomic number from mass number

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11
Q

whats an isotope

A

when atoms of the same element have diff nos of neutrons

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12
Q

what did the ancient greeks believe about atoms?

A

everything was made of atoms. atoms were tiny spheres which couldn’t be divided

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13
Q

why was the discovery of electrons important

A

it showed atoms are NOT spheres that can’t be divided. they have an internal structure.

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14
Q

what was the plum pudding model

A

ball of positive charge w/ negative electrons embedded in it

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15
Q

describe the finding of the alpha particle scattering experiment

A

most particles went straight through the gold meaning atoms are mostly empty space (pp models wrong)

some atoms were deflected meaning centre of the atom must have a positive charge that repelled the alpha particles

some particles bounced straight back so the mass of the atom must be concentrated in the centre.

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16
Q

what did scientists replace the plum pudding model with?

A

The nuclear model

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17
Q

what did niels bohr sugges t

A

electrons orbit the nucleus at specific distances (now called energy levels)

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18
Q

why was niels bohrs theory accepted?

A

Bohrs work agreed with the results of experiments by other scientists

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19
Q

what was the order of discovery?

A

electrons, protons, neutrons

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20
Q

what is radioactive decay

A

when isotopes have an unstable nucleus so the nucleus gives out radiation to become stable.

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21
Q

radioactive decay is a _____ process

A

random

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22
Q

what is activity and what unit is it measured in?

A

the rate at which a source of unstable nuclei decay

measured in becquerels (Bq)
1Bq = 1 decay per second

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23
Q

what is the countrate

A

the number of decays recorded each second by a detector .

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24
Q

whys the countrate different to activity?

A

Background radiation

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25
Q

whats an alpha particle

A

a helium nucleus

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26
Q

whats a beta particle

A

an electron which is ejected from the nucleus at a v high speed

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27
Q

how is a beta particle formed

A

inside a nucleus when a neutron changes into a proton and an electron

28
Q

whats a gamma ray

A

type of electromagnetic radiation from the nucleus

29
Q

whats alpha particles range in air

A

alpha particles are large meaning they can travel around 5cm before they collide w air particle and stop

30
Q

how far can beta particles travel in air

A

beta particles can travel further than alpha,, they can travel 15cm before stopping

31
Q

how far can gamma radiation travel

A

several metres before stopping (further than both alpha and beta)

32
Q

what are alpha particles stopped by (penetration)

A

a single sheet of paper

33
Q

what are beta particles stopped by

A

a few millimetres of aluminium (more penetrating than alpha)

34
Q

what are gamma rays stopped by

A

several cm of lead (most penetrating)

35
Q

what does ionising mean

A

when radiation collides with atoms, that can cause the atoms to lose electrons and form ions

36
Q

what does it mean to be strongly ionising

A

can produce a lot of ions when colliding with material

37
Q

order of ionising ability:

A

alpha: v strongly ionising
beta: quite strongly ionising
gamma: weakly ionising

38
Q

during alpha decay the atomic number____

A

decreases by 2

39
Q

during alpha decay the mass number ____

A

decreases by 4

40
Q

during beta decay the atomic number____

A

increases by 1

41
Q

during beta decay the mass number ____

A

does not change

42
Q

in gamma decay, both atomic number and mass number______

A

do not change

43
Q

what is the half life

A

the time it takes for the number of nuclei of an isotope in a sample to halve.
OR
the time it takes for the count rate (or activity) from a sample containing an isotope to fall to half its initial level

44
Q

whats the risk of ionising radiation

A

can increase the risk of cancer in humans

45
Q

what is Irradiation?

A

irradiation is exposing an object to nuclear radiation (eg sterilisation)

46
Q

why would an object that needs to be sterilised be placed in a plastic wrapper?

A

to stop bacteria from entering after sterilisation

47
Q

when using gamma radiation to sterilise an object, why would you use a lead shield?

A

to protect the workers

48
Q

how does gamma radiation sterilise objects?

A

by killing any bacteria present

49
Q

why does an object thats been sterilised with gamma rays NOT become radioactive?

A

Objects come into contact w/ radiation but not radioactive isotope itself

50
Q

what type of shielding of shielding should you use for the types of radiation

A

alpha- gloves
beta & gamma- lead apron
(lead walls / lead- glass screen)

51
Q

what can we use a radiation monitor for

A

to measure how much radiation a person has received so we can stop them from working with radioactive isotopes

52
Q

whats radioactive contamination?

A

when unwanted radioactive isotopes end up on other materials

53
Q

why is radioactive contamination hazardous?

A

atoms decay and emit ionising radiation

54
Q

when would alpha radiation be very damaging?

A

if inhaled or swallowed

55
Q

what are the natural sources of background radiation

A

certain rocks including granite. (Cornwall suffers)

cosmic rays

56
Q

what are cosmic rays

A

cosmic rays are v high energy particles which travel through space and crash into earths atmosphere

57
Q

what are the man made background radiation examples

A

nuclear weapon testing
nuclear accidents

58
Q

what can your exposure to BR be affected by

A

location and occupation

59
Q

to check the function of the thyroid gland, what does the patient drink?

A

solution of radioactive iodine

60
Q

what does radioactive iodine emit?

A

gamma radiation which passes out of the body and can be detected

61
Q

what are the issues to consider when using a radioactive tracer

A

must emit radiation that can pass out of the body and be detected , must not be strongly ionising so it doesn’t cause damage, must not decay into another radioactive isotope and must have short half life so isnt in body for long time.

62
Q

whats the benefit of using a radioactive rod to treat cancer?

A

placed very precisely next to tumour and there’s less damage to healthy tissue

63
Q

what is nuclear fission?

A

when the nucleus absorbs a neutron, it splits, forming two daughter nuclei , emitting two or 3 neutrons + gamma radiation & releases energy

64
Q

what happens to the neutrons emitted during fission?

A

can now be absorbed by more uranium nuclei and trigger fission again (eventually called chain reaction)

65
Q

what is an explosion in a nuclear weapon caused by?

A

uncontrolled fission chain reaction

65
Q

whats a controlled chain reaction used for

A

releasing energy in a nuclear reactor

66
Q

what happens in nucleur fusion

A

2 light nuclei join to form a heavier nucleus. Some of the mass of the nuclei can be converted into energy which is released as radiation. NOT. a chain reaction

GCSE Physics <3 (12 decks)

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